This invention relates to an apparatus that measures light transmitted through a fluid sample and in particular to an apparatus that provides a direct readout of transmitted light.
For monitoring air which workers are exposed to during a work period, workers wear chemical badges that are pouches filled with a chemical solution which will absorb certain gases such as sulfur dioxide or nitrogen dioxide. At the end of the work period, the badges are turned in for analysis. To analyze the badges, sealed packets of reagents contained in the pouches are broken and mixed with the chemical solution. If a gas has been absorbed in the chemical solution, the solution changes color. A photometric analysis of the solution is then done and the results recorded. If a worker has received an excessive dosage of a certain gas or the accumulative dosage exceeds a given safe level, the worker is not allowed to work in an area that contains the gas for a prescribed time.
A photometric analysis apparatus has been used to measure light transmission through fluid samples as shown in Carter U.S. Pat. No. 4,066,362 issued Jan. 3, 1978. While this is an excellent apparatus, it does not readily lend itself to an average plant operation since care must be taken to avoid leakage of outside light in the area in which the sample is positioned and no provisions are made to readout data directly in units established by industrial and government agencies. The apparatus of this invention avoids the aforementioned problem and reads out photometric analysis data directly over a wide range in established units.